Field of the Invention
The invention relates to an arrangement for connecting a high-voltage or very-high-voltage power cable to an equipment element.
Description of the Prior Art
A power cable includes, around a conductor, from the inside toward the outside, an insulative layer, a semiconductor layer, a metal shield and an insulative external jacket.
To connect a power cable to an equipment element, for example a cable splicing element or a cable termination element, the external jacket is removed over a certain length, a welded joint is effected between the metal shield of the cable and a metal shield of the equipment element, and a connection element is disposed between the cable and the equipment element with one of its ends in contact with the external jacket of the cable and its other end in contact with the external surface of the equipment element.
The connection element includes a length of heat-shrink sleeve applied longitudinally in this way between the external jacket of the cable and the external surface of the equipment element. A layer of mastic is conventionally disposed radially between this length of heat-shrink sleeve and the elements consisting of the metallic shield of the cable, the external surface of the equipment element and the welded joint.
The above kind of connection arrangement gives rise to the following technical problem.
The insulative external jacket of the cable is traditionally extruded. Because of this mode of fabrication, it has a greater capacity for shrinkage than a molded sleeve. Moreover, high-voltage and very-high-voltage cables carrying large amounts of energy, and which are therefore heavy, are made from a high-density elastomer material, for example high-density polyethylene, which by virtue of its composition has a greater capacity for shrinkage than a low-density or medium-density elastomer material.
Following shrinkage of the external jacket of the cable, which may entail forces of several tonnes, the external jacket may become detached from the connection arrangement and the metal shield of the cable may be exposed, which compromises correct electrical operation following the loss of insulation. The ability of the metal shield to withstand voltages and lightning strikes is therefore reduced.
This shrinkage of the external jacket of the cable may also damage clamp type cable retaining arrangements in which intermediate layers of neoprene intended to absorb radial expansion may escape from the clamp, because the coefficient of friction between neoprene and polyethylene is higher than that between neoprene and the metal of the clamp.
The invention solves this shrinkage problem by proposing an arrangement for connecting a high-voltage or very-high-voltage power cable to an equipment element that retains the insulative external jacket of the cable against shrinkage forces inherent to its construction.